In a large bowl of an electric mixer, cream the granulated sugar, brown sugar, butter, and peanut butter on low speed. Beat in the egg, milk, and vanilla.
Sift the flour, baking soda, and salt on a square of wax paper (or mix in a bowl). Stir into the sugar mixture and mix thoroughly.
Shape into 40 walnut-size balls. Roll in granulated sugar in a small bowl. Place on an ungreased cookie sheet and bake for 8 minutes.
Remove from the oven and immediately press a chocolate kiss into each. Transfer the cookies to a wire rack to cool.
Spread on top of Peanut Butter Cookies.